To date, magnetooptic media have been notorious for surface or other media defects. The problem is sufficiently severe that every storage member employing magnetooptic recording should be surface analyzed for defects before data is actually recorded. Such surface analysis involved placing each storage member, such as a rotatable disk, into a recorder. The media is then written and read for defects for identifying the areal location of the defects and then the media is erased. Finally, those tracks with defects are marked for location of the defects as is known. It is desired to reduce to number of disk rotations or storage member movements in achieving the surface analysis, i.e. combining the read and the erasing.
It also has been the practice in magnetooptic recorders to take three rotations for updating data in place. The first rotation is to read the data and store it in an external memory. The second step is to erase the area to be rerecorded and the third rotation is to record the data. It is desired to reduce the number of rotations necessary for recording and for enabling update in place, i.e. changing certain data without erasing other data unnecessarily.